Implantable microelectronic systems can provide improvements in a person's health status, by monitoring and correcting existing medical conditions, or by providing substitute capabilities for normal bodily functions that are damaged or cease to operate. A number of implantable microelectronic systems are currently in use, including cardiac pacemakers and implantable cardioverter defibrillators that monitor heart rhythms and deliver a corrective electrical signal if a dangerous cardiac rhythm is detected (see http://www.nlm.nih.gov/medlineplus/pacemakersandimplantabledefibrillators.html), cochlear prostheses that provide hearing function to some who have lost normal hearing (see http://www.nidcd.nih.gov/health/hearing/coch.asp), and vagus nerve stimulators that can be used to correct or to treat certain conditions (see http://www.mayoclinic.com/health/vagus-nerve-stimulation/MY00183 that describes treatment of depression and http://www.epilepsy.com/epilepsy/vns that describes prevention of epileptic seizures).
Recent advances in the field of neural prosthetics have demonstrated the thought control of a computer cursor. This capability relies primarily on an electrode array surgically implanted into the brain as an acquisition source of neural activity. Various technologies have been developed for signal extraction. However most suffer from either fragile electrode shanks and bulky cables or inefficient use of surgical site areas.
Among current neural prosthesis technologies, some have well controlled metal electrode fabrication and circuitry integration techniques but have designs that are brittle and difficult to handle. Some have reliable interconnect cables but are weak on IC expansion capability.
An important goal in neural prosthesis is to be able to decode the movement intention in the parietal cortex from neurons by implanting neuroprobes. While 3-D integrated silicon probes have been successfully manufactured, the degradation of the signal to noise ratio (SNR) is still a major challenge because electronics are too far away from the recording site. Additionally, recent development in bioimplantable devices such as retinal, cochlear and cortical prosthesis implants also increases the demand for totally implanted technologies.
Recent achievements in silicon probes implantation in the parietal cortex have enabled technological advances in neural prosthesis research. However, current state of the art technologies still suffer from high signal-to-noise ratio and complicated IC integration schemes.
In recent decades, integrated wireless microsystems have provided tremendous opportunities in neural prostheses by establishing an artificial interface to the central or peripheral neural system. For example, retinal implants have been studied for the treatment of outer retinal degenerative diseases, such as age related macular degeneration (AMD) and retinitis pigmentosa (RP). However, many technologies are still in development and few have actually been transferred to the clinical practice due to constraints in material biocompatibility, device miniaturization, and flexibility.
There is a need for a totally biocompatible packaging/integration technology. There is a need for an easy and precise way to electrically connect and assemble various semiconductor chips and pre-manufactured discrete components to provide a functional biomedical system. There is a need for a simple way to electrically connect a large number of connections (e.g., more than 100 interconnections) between chips.